1. Field of the Invention
This disclosure relates generally to ventilating range hoods and, in particular, to a device that senses the air for the presence of certain hazardous elements and controls a variable speed fan in response to those elements, in such a way as to increase the comfort and safety of the surrounding area.
2. Background
Modern homes are being built with increasing emphasis on energy efficiency. This generally means more thermal insulation, more vapor barriers and better quality seals around windows and doors. This type of construction has given rise to the concern that ventilation may be inadequate, in light of the need for a continuous supply of fresh air and concerns about volatile byproducts of manufacturing of synthetic items. There is further concern in the many homes that use combustible fuels for heating and cooking or lighting. In addition to the psychometric comfort factors of heat and humidity and the essential need for oxygen, there are the serious health factors of carbon monoxide, smoke, and any other products of combustion deriving from these activities. Excess heat and humidity in an enclosed structure can also be quite destructive to the structure itself, leading to problems ranging from mildew, to insulation failure, to deterioration of the actual structure itself through attraction of insects and rot.
In 1998, there were approximately 200 deaths and 5000 injuries attributed to residential, non-vehicle, carbon monoxide (CO) poisoning in the US. While equipment malfunctions, such as cracked heat exchangers played a role, a key factor in all of these injuries and deaths was inadequate ventilation. Roughly 10% of these casualties have been attributed to gas stoves and ovens. Low-level cases are more difficult to track, since the symptoms are similar to common cold or flu, but are likely to have a much higher occurrence. Thus, considering the impact of lost work days and reduced activity due to illness for low-level exposure, and the injury and death resulting from high level exposure, the cost to society of inadequate ventilation in conjunction with combustion appliances is substantial.
The ASME standards for gas stoves, which allow for trace amounts of CO, are based on the assumption that the stoves are vented. However, many are not and even those that are generally use a range hood with a fan that must be switched on manually. Many people do not turn these venting fans on unless there is detectable smoke or odor or if the kitchen becomes excessively hot. In other words, kitchens are often inadequately ventilated to a degree that may be a health and safety concern.
In the case of CO, which, being colorless and odorless is undetectable without some sort of electronic device, it is difficult to detect CO being emitted by a cooking appliance since the installation instructions for plug-in detectors recommend placing them a minimum distance away from such appliances so as to avoid setting off an alarm due to transient levels emitted from said cooking appliances. The alarms, being on/off devices must receive some minimum level of contamination before activating the alarm. The alarms are useful for notifying building occupants of the hazard although they do nothing beyond this to ameliorate the situation. The same is true for smoke detectors as well.
The device disclosed herein was invented to address these concerns, by providing an inexpensive, automated and effective response to the presence of the factors of heat, humidity, CO and smoke and smoke or other similar hazards in a kitchen as the result of cooking or introduced by some other means.
A variety of range hoods have been developed in an attempt to provide ventilation of cooking related exhaust fumes and other volatile waste products. Examples of such devices are found in U.S. Pat. Nos. 4,133,300, 4,614,177, 3,125,869 and 3,359,885. While these and other devices represent improvements in the art of ventilating heat and fumes generated by cooking food, they fail to provide the automatic safety features enabled by the current disclosure.
U.S. Pat. No. 2,807,994 to Samuel M. Bernstein, issued Oct. 1, 1957 combines a ventilating range hood with an exhaust fan. U.S. Pat. No. 3,690,245 to Ferlise, et al, in Sep. 12, 1972 provides a range hood in which the fan can be automatically switched on when cooking is detected by means of built-in thermostats. The fan is also switched off in the presence of fire. The fan is set to switch on when the temperature in the duct exceeds 140° F. which indicate that cooking is taking place. If the duct temperature exceeds 2408° F., the fan is shut down on the assumption that there is a fire.
U.S. Pat. No. 5,186,260 to William Scofield, issued Feb. 16, 1993 discloses a range hood with a wire heat sensor which triggers a fire extinguisher if excessive temperatures are detected. U.S. Pat. No. 5,207,276 by the same inventor, improves upon the fusible link triggering system with the use of an explosive squib.
U.S. Pat. No. 5,232,152 to Richard Tsang, issued Aug. 3, 1993 shows a range hood connected to a humidity sensor. The fan is automatically activated if the humidity exceeds a certain preset level. The patent allows for a remotely located sensor in addition to a sensor integrated into the hood. The hood allows for both automatic and manual modes of operation.
Automatic ventilating systems that respond to temperature and humidity have been disclosed in the area of general ventilation, as well in systems that are responsive to smoke. U.S. Pat. No. 6,053,809, to Henry Arceneaux, issued Apr. 25, 2000 automatically raises a building ceiling panel in the presence of smoke and activates an optional fan. U.S. Pat. No 5,810,244 to Ngai, issued Sep. 22, 1998 describes a ventilating fan controlled by both temperature and humidity sensors using a microprocessor controller. U.S. Pat. No. 4,726,824 to Staten, issued Feb. 23, 1988, describes a building level system for indoor pollution control which utilizes air quality sensors to monitor for various pollutants including carbon monoxide. The system has a display which indicates the presence of these unwanted pollutants and responds to their presence by conditioning the air by means of a variety of filters. U.S. Pat. No. 5,976,010 to Reese, et al, issued Nov. 2, 1999 describes an energy-efficient building level system for indoor air quality that senses the carbon dioxide level in a room and if an undesirable level is detected, actively reduces that level by mixing the air with air from other rooms.
And plug-in or battery operated smoke detectors and carbon monoxide detectors have become as popular residential safety items. U.S. Pat. No. 6,426,703 to Johnston, et al, issued Jul. 30, 2002 describes a smoke and carbon monoxide detector that are combined and integrated into a single unit. Like the myriads of individual detectors devices available, this device will issue an alarm if either smoke or carbon monoxide is detected.
While the above-described devices are effective for their intended purpose, there is nevertheless a need, and a consumer desire, for an improved range hood that responds automatically to the various airborne hazards found in the a kitchen, particularly carbon monoxide and smoke which actively purges these hazards rather than just sounding an alarm and utilizes a smart controller to ensure the appropriate response to multiple, sometimes conflicting signals. The net result is a ventilating exhaust fan that consistently provides the appropriate operating speed as well as an alarm to be sounded if the hazard levels become dangerous despite the fan action.